Yes, definitely! In fact, you <em>should </em>say 'he' or 'she' in this case.

It is absolutely normal to call pet animals 'she' or 'he' according to their gender. In fact, people would think it very odd if you referred to your dog as 'it'. Nobody uses 'it' for their own pets: saying 'it' about your pet dog would sound very strange, cold and detached.

NB Russian grammar books seem to be full of myths and misinformation about how we do (or don't) use gendered pronouns in English.

For your own pets or pets you know or are aware of the gender, yes it is natural and normal to say he or she.

To enquire about the gender of an unknown pet or baby it is ok to ask "what is it? a boy or a girl?", if it is unclear or you are unable to see for yourself easier for dogs and pets that don't wear clothes; than for babies who do.

Yes yes yes, we call creatures by gender if we know it and especially the closer they are to us, so, family pets are very much named and the gender is known. Nearly everything else is an "it", except boats which are female.

It is very common in English to refer to an animal as he or she, especially if it is a pet. In fact I don't know anyone who refers to a pet as it.

Да, все всё поймут. Утешу вас: англоязычные товарищи не настолько бессердечные, как их малюют, так что они и сами распрекрасно называют животных "он" и "она". Тем более когда дело касается их собственных питомцев. Посмотрите, например, с какой готовностью все в этом видео (ну, кроме хозяйки черепашки, но ей по роли положено) стали называть черепашку "he" (пол черепашки обозначен в самом начале):