You're welcome. Glad you enjoyed it.
1) When the creature starts to eat the guy by drenching him in the acids, would it liquefy the flesh first before the clothes?
Yes, the clothes would be more resistant.
2) Is there any part of the guys body that it would enjoy feeding on more than the rest once liquefied?
In this case, no. The Devourer has to suck the liquid up as fast as it forms. Otherwise it will all just end up a puddle on the floor. He will just suck it up as quickly as possible, and blood, muscle, and fat would all blend to one flavour and texture.
3) would it liquefy the guys tight jeans before it set to work on his private parts , how long it take to deal with the jeans and slurp them up?
The jeans would probably be liquefied after the private parts, but even they would go quickly because of the strength of the acids. The Devourer isn't conscious of what he is doing at each step. He just regurgitates those acids and then slurps fast to get everything.
3) What would happen to the button at the front of the jeans and the zipper etc.?
The metal parts wouldn't liquefy. They'd drop to the floor, slightly corroded. The Devourers would later get rid of them, since they wouldn't want metal in their soup.