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How can I display OSM maps in Flutter 'Web'?

I'm trying to create a custom map using Flutter Web that would be capable of displaying custom statistics for a place for COVID-19.
First we'll have a interface that display statistics for our entire planet:
https://google.com/covid19-map/?hl=en (Just like htisw)
Then the user can click on any country to zoom-in with probably an ease-in transition to see the number of cases in each state or province of that country. Assuming that I am able to fetch the exact co-ordinates of the epicenter in that country, I would like to deepen the shade in those parts in such a way that it lightens out as we move towards areas which have a lower number of cases.
Is it possible in Flutter Web?
I came across this plugin (thanks to this thread on SO Openstreetmap in Flutter?)
https://pub.dev/packages/flutter_map
but it doesn't explicitly say that it supports Flutter Web.
I tried fetching the tiles from OSM(Open Street Map) and displaying the maps on Flutter Web with the help of the example given in the above site https://pub.dev/packages/flutter_map#open-street-map-provider
But it didn't really display anything, maybe because a certain widget or function didn't work as expected.
According to your experience, which is the best way to achieve what I am looking for?
If possible, please describe the answer in such a way as if you were me and trying to do what I am doing.

Flutter_map doesn’t support flutter web.

You may check out the below Flutter Maps widget which has support for all the platforms including web.
https://pub.dev/packages/syncfusion_flutter_maps
Regarding the requirements you have mentioned, you can try the below things.
By dynamically changing the focal point and zoom level based on the click position, the easing effect can be achieved.
https://help.syncfusion.com/flutter/maps/zoom-pan#update-the-zoom-level-programmatically
With the combination of dynamically adding shape sublayers on top of the tile layer and color mapping for that shape sublayers, you may achieve this.
https://help.syncfusion.com/flutter/maps/shape-sublayer#shape-sublayer-on-tile-layer
https://help.syncfusion.com/flutter/maps/shape#range-color-mapping

Checking if object in Open Street Maps is a building

I'm using Leaflet library in my ReactJS app and I wonder if there is a simple way to recognize if object clicked by user is a building.
Idea that came up to my mind is to check map colour under clicked position.
Does it make sense?
I appreciate your help.
Colleagues in comments advised to give some use-case:
App I'm working on is meant to mark antique buildings with elevation in bad shape so city architecture management had simpler job of searching for them.
Every user of this App can mark such building. To prevent hooligans from corrupting data with senseless points on map I wanted to validate as a first step if clicked point is a building.
I hope it will clarify problem a little bit.

I wonder if there is a simple way to recognize if object clicked by user is a building.
No.
You basically want to run arbitrary point-in-polygon queries against OSM's building dataset, and I will presume that you don't want to host that dataset yourself.
The simplest way to do this is to perform queries to an Overpass API server, passing a is_in query and filtering by the building tag key. The OSM website's query feature functionality uses such a technique.
With this technique you won't have to worry about hosting the data, just about creating the right Overpass API query. Please bear in mind that the Overpass API servers are run by volunteers and their resources are limited.
The second simplest way would be to download a OSM extract of you area of interest, and run the point-in-polygon queries yourself, by whatever means you like (PostGIS' ST_Intersect, turf.js, etc etc).
If you will be using Leaflet, another approach would be to use vector tiles, and set it up in such a way that the buildings thematic layer is interactive. This will require you to be aware of the limitations of the vector tile servers.
Idea that came up to my mind is to check map colour under clicked position.
That is unreliable. Think about labels on top of buildings, or the colour of the edge of the building area, or buildings that don't render with the standard colour (e.g. places of worship, monuments).

choose language to draw map & show few ares with an icon

I am new to web technologies, I started looking into HTML, CSS, Java script (I am familiar with these now).
Now I wanted to draw a map (ex: google maps of a certain city) & want to mark my own locations (ex: I want to show all petrol bunks in my city with small petrol bunk Icon) .
So for the above requirement what language and technologies I can use.
can above thing be achieved with the help of HTML & Java script. or do I need to learn & use any other thing. my apologies if i use wrong terminology I am new to web technologies.
Please suggest.

The easiest way to draw interactive map of fuel sites in your city is using google maps api. You should start here https://developers.google.com/maps/documentation/javascript/
And javascript is definitely the language you are looking for. You also gonna need coordinates of every fuel site in your city
this is my example of such map:
https://www.google.com/maps/d/u/0/viewer?mid=1DLGEGzVNBf7IbKZ1h1j-wdI4-vA
I created it using google maps constructor and than placed it on my client's site.

Tile-based map solution supporting vector layers

I need to display a map of the US and, above that, a layer of states, another of counties and another of places (as per defined by US Census). Also, depending on some criteria, I need to dynamically toggle one layer or another, and to colorize some parts of the layer (e.g. fill some counties in red, others in green, etc). The map itself can be plain simple, I don't need roads or anything that detailed.
My first attempt was done with d3 based on this example, but I'd really like to switch to a tiling-based solution as it seems more responsive, lightweight, smoother and better supported for mobile devices.
I've been looking on the web for a solution (commercial and non-commercial, as a service or locally implementable) but I haven't found one to fulfill all my needs. For example, I've found MapBox which even has a very nice editor, but you can't fine-control the layers you define. I can hide/show a layer, but I can't colorize just a part of it. Google Maps was of course my first option but I didn't find a way to do as above.
Do you know if is there any solution out there that I could use?

I would have a look at the products supplied by boundless. They enable you to use a wide range of technologies and provide the final product in a number of ways. They use Geoserver as a tiling server into which you can output tiles or features depending on what your needs for that layer is.
You can connect to it using ESRI, Quantum GIS or use the included web based map. They are open source so there is a community version that can be used for free or a commercial version that is basically the same but comes with enterprise support.
You can find them here.

how can i create a dynamic map that shows our company locations?

I'm searching for a jquery plugin that allows me to create a dynamic world map and mark the countries that we have a branch there in a different color or put a logo of our company on that country.
I need to have access to that map so when a user clicks on a country i can fire a jquery event.
i think Google has something like this but I'm not sure
Thank you

I'm not quite sure what is your intention. But think you may draw your attention follwings.
http://www.gethifi.com/blog/jquery-vs-flash-for-interactive-map
http://code.google.com/p/jquery-ui-map/
http://jquery-ui-map.googlecode.com/svn/trunk/demos/jquery-google-maps-basic-example.html
http://jqvmap.com/
http://jquerygeo.com/test/examples/events.html
These are the best I found so far