Yes we have vosotros (in Spain) or ustedes (in the rest of the Spanish-speaking world -can't speak for Equatorial Guinea though). But we don't call it a 4th person pronoun. It's just the plural form of the 2nd person pronoun:

1st singular: I / yo

1st plural: we / nosotros

2nd singular: you / tú, vos, usted if you wanna be formal

2nd plural: plural you, y'all / ustedes, vosotros

3rd singular: she, he, singular they / ella, él, elle (that last one mostly used among the young queer/progressive community in some countries)

3rd plural: they / ellos, ellas, elles (same above)

Don't know what a 4th person pronoun would be. And I'm a Spanish teacher in South America lol

Yes! Just don't say vosotros in Mexico or they'll think you're a dork