Question: If you receive an offer of employment and you accepted it does it mean that you are hired as is?

Yes, you are hired as is. but because expediting such documents that will require you to undergo for the whole process meant tiresome to wait longer than as expected, you can look for some else oppurtunities.

However, that matter must be referred to your local agency who hired you, there is no absolute rule we should have to based on as to wether you can freely accept else job offers.

if they told you YES, then you have to wait.
otherwise, then look for another oppurtunities,
or make a choice whichever comes first or for the later.

Decide only to choices favourable to you...

x men