More than likely yes.
by mounting it
the dog can impregnate a female in less than 5 months of it life
Simple- he can't.
yes, they can have threesomes
Not unless some form of artificial insemination is being used to impregnate them. Female guinea pigs cannot self-impregnate.
Probably yes. Male Bobcats have been known to impregnate female domestics.
yes it does not mater the size but if they love ether.
No, cats and dogs have a different amount of genes.
Extremely likely.
The function is to impregnate the female with sperm, and reproduce off-spring.
Anatomy! The only way for the male to impregnate the female is if he is on top. His penis cannot reach her vagina from any other position.
No. Only a male can impregnate a female. No female mammal of any species can get another female pregnant. For mammals that have a "heat" cycle, being in "heat" is required for pregnancy by a male. If such a mammal (a dog for instance) is not in heat or doesn't have a male partner, pregnancy is not possible.