Everyone is right, modern fuel goes off very quickly (more so in small quantities) and the carbs dry out reasonably quickly when left for any length of time and the fuel leaves a horrible yucky glaze behind which blocks jets and airways.
These should help you get the float bowls off but I would give the screws a good squirt of release spray and allow to penetrate before attempting to remove them as they are indeed made a cheese like material- possibly Dolce Latte?
https://www.ebay.co.uk/itm/US-PRO-To...wAAOSwqWZdMEfy
If they hint at getting rounded off I would stop and try and get a pair of pliers on them if you can to start them off.
Also if you're not familiar with CV carbs take care when handling the diaphragm when you remove the slide as they can be easily damaged.
And finally, have a nice clean work area with some little pots (rattle can lids are ideal I find) for putting the bits in as You dismantle, clean then reassemble one carb at a time.
Enjoy
