oil and drain plug question

I have been told to put 1.8 litres in my bike which is about 2 quarts but I read on here that it is 1 quart.
Which one is correct??! I have done about 10 miles on the bike with 1.8litres in it and want to know if I have damaged it if I have got too much oil in it.

Also I read that you are not supposed to remove the front drain plug (hex head) as it holds the shifter in place?
I have been removing both when draining the oil, is the reason for gear shift issues and neutral light coming on?

Thanks in advance for advice.

Now that's going to make it way too easy.

In another thread he said it's a '99 Husky.

sorry stupid me?
yes its a 1999 610SM