Whether fertile or not, if the penis was briefly entered in the vagina BUT with 4 layers of clothes in between, is pregnancy likely? Or a risk?

Listen. . Any entry is a risk. Even condoms aren't 100%. Certainly, clothing is not a barrier to semen, even 4 layers. Possible risk, but doesn't sound likely at all....unless ejaculation happened, then the risk is higher, tho still unlikely unless semen traveled to top layer. Good luck...use a condom instead.
Yes. If you have sex, even briefly, a woman can get pregnant. You should take a pregnancy test in 7 to 10 days. If it is positive, then get prenatal care started. If it is negative, then repeat the test in one week. If it is then positive get prenatal care started, if second test is negative then you are probably not pregnant. Those who have sex will be called parents!