About your first question,

This is my output:

> 1+1
2

Now for your second question, this snippet should give you an error something like this:

> const n: number = "string"
<repl>.ts:7:7 - error TS2322: Type 'string' is not assignable to type 'number'.

You can try:

> const n: number = 5;
undefined
> n
5

I can't find any solution to your problem, you should try reinstalling the typescript again