jQuery 1.x and 2.x are there strong differences in browser support for features?

Question

JavaScript

I know that the difference between 1 and 2 is that in 1 there is support for older browsers and in version 2 there is no support. I'm right?

The question is, what features will not work in older browsers if you use version 2?
for example in ie7
Most likely selection by id will work and other obvious functions too.
And what functions will not work then?

I have a choice in versions 1 or 2 for a project that needs some kind of support for older browsers, but at the same level of importance is the speed of the scripts. Help in this difficult matter, dear Toasters!

Answer 1

If you need support for ie6-7-8 then the first version is your choice anyway.
If not, use the second one. But you will hardly feel the difference in speed in typical tasks.
Also, check which version of the plugins you are going to use are compatible with.