Which bacteria do not exist in colonial forms?

Mycoplasma can live successfully in the phloem due to being:

The given characters are seen in which of the following group?
$(i)$ Unicellular,colonial,filamentous,symbiotic or free living.
$(ii)$ The colonies are surrounded by a gelatinous sheath.
$(iii)$ Some can fix atmospheric nitrogen in specialized cells called heterocysts.
$(iv)$ They often form blooms in water bodies.

The cyanobacteria are also referred to as

What is the primary function of a heterocyst in cyanobacteria?

In the five-kingdom classification,actinomycetes are included in: