Is is alright for a 22 year old to flirt with, talk about dirty things like oral and sex?

No, that is illegal. Stop it.

No, it is not all right. If you are the 22 year old you should be aware of how explosive that is. Don't risk getting a sex offender label for life.

No.

No, it's called "child annoyance," an offense requiring lifetime registration as a sex offender.

No. It is a crime called contributing to the delinquency of a minor. It can put the person in jail and on the sex offender registry.

I assume when you say "alright" you mean is it legal. The short answer is no. Probably. But much depends upon the circumstances and the actual content of the texts. I suppose one argument is that the actual content is fairly tame. It may also depend on whether the 15 year initiated and/or encouraged them, or is freaked-out by the overtures, and/or will turn on you if parents or guardians find out and become furious (at you). However, I wouldn't continue such communications at the present time if I were you. Under the current statutory structure, a fifteen-year-old is considered incapable of consenting to sex. One favorite prosecutorial claim, often substantiated, is the these messages are part of a scheme to "groom" someone for sexual encounters. The 7 year difference in age is also a problem that suggests the older person exploited a much younger person. Why not find as the target of your affections someone closer to your own age and definitely over 16 years old or wait a few years before taking this relationship where it seems to have already been.

That is enticing a minor and you will be arrested for a felony and possibly be convicted, making you a registered sex offender for life. I advise you to stay away from minors before you get a long prison term.

No. At the least is is child annoyance which can be a felony and a sex registration issue.