The questions are simple, but offered solutions are not very good.

The one for Question 5 is even wrong - for the number 8 this should return (4, 4) because 4 is in the list twice...

Python is a nice language to demonstrate your understanding of appropriately using data structures to efficiently solve the problem at hand. Interview questions which are not language specific arent really looking for flawless code, they are trying to assess your problem solving skill set.

I just went through interview loops for MS, FB, Google and a few others. I've found that the answer to your question is that language is largely irrelevant, but it depends.

On all of my interview loops, interviewers clearly told me that Python was no problem. Usually they'll tell you that they might not know Python that well and that maybe you'll have to explain some specific constructs to them. But that you can proceed with Python, no problems.

Which I've found largely true. I can confirm my MS and FB interviews went fairly smoothly even though neither company uses Python very much.

There's a company giving me trouble though, and that is Google. For some reason, even though interviewers assured me I could choose any language, I'm having some problems with some committees particularly regarding Java.

With that said... Python is so much easier to code in, it might still be an advantage. But choosing the company language might be an advantage too in some cases... So it's a hard question. I'm personally probably staying with Python and regarding the Google experience as an outlier, but it's hard to say.