On the basis of structure polymers are classified as-

(i) Linear polymer: These polymers consist of long and straight chain. Examples includes high density polyethylene (HDPE), poly(vinyl chloride) (PVC), etc.

(ii) Branched chain polymers: These polymers contain linear chain having some branches. Examples includes low density polyethylene (LDPE), glycogen, etc. (iii) Cross linked or Network polymers: These polymers have some crosslinks between various linear chains. Examples are Bakelite, melamine, etc

and formaldehyde

OK. !!!

You are Correct.

Classification of polymers based on their structure can be of three types: (Application of each is shown below)

(i) Linear polymers Application:

This polymer is largely used for making electric cables and pipes.

(ii) Branch chain polymers Application:

Low-density polyethene (LDPE) used in  plastic bags and general purpose containers is a common example.

(iii) Crosslinked or Network polymers Application:

Bakelite used in electrical insulators, Melamine etc.

I hope I have answered your question.

With Best Wishes,

Samir G. Pandya