Question 1.
Yes you can by using a “Punnett square.” Counting the squares that have each combination. You can also use the Punnett square for dihybrid crosses they have 4 alleles each.
Question 2) You divide the number of boxes with a dominant allele by 4 and multiply your result by 100 to get the percent.
I hope this is right, I haven’t done this in awhile. Please let me know if y am correct. I hope this helps.