The visa is a document (a sticker) which allows you to enter the country under specific conditions (time, before a date, with/out work... )

In the very moment you enter you receive a PERMISSION OF STAY under/according to the visa. Then you stay in a permission of stay, NOT stay in a visa.

When you extend, you get an extension of permission of stay.

I think it's a bit tricky...

You should inforrm 24 hours after changing address/returning to country. If you stay in hotels, they should inform the TM30. And when you arrive at CM at your home, you update the last TM30 "to the same address".

But it's tricky because in the office they say "only when travelling abroad"...

I think the best is to go and ask. But not sure what will happen if any of the hotels in the way didn't report in time... :/

And she is asking about the TM30, not the 90-days report...

The 90days report can be done 15 days before to 7 days after the date. But it has NOTHING to do with overstay.

If you're talking about extending, not reporting, then you can do it up to 30 days in advance - even 45 in some provinces, I think. So not needed to wait until last day. If the limit date is on Sunday or official holiday you can do it the very next day without any overstay but if anything goes wrong you'll get an overstay so no point in not do it in advance. Just do it tomorrow.

Don't need. Contract and signed copy, and passport and signed copies of the relevant pages. The TM30 should be done, but AFAIK is not needed to show - but if you have it, better to show it with a signed copy.

Yes, on Monday and Thursday there are loads of people because of the agencies. I usually go by around 9am and the queue is less than 15 or 25 minutes in total. Some day went near the end, near 11am, and there were even less people.

That's usual for a Monday.

I always went on Wednesday or Friday and never saw more than 100 people in queue.

Twice a year

If the law says "money in cash" it doesn't mean "cash, well, or any other thing you want".

It's only cash. Period.

When everyone says "cash only" it means cash only, not "cash only, well, or a bank statement or something".

Cash. Only cash. Period.