1. 遅れる(おくれる)
2. おくれる is a verb, means "to be late".
おそい is an adjective ( or おそく is an adverb ), means "late" or "slow"
3. see examples here, it's a on-line japanese-english dictionary:
http://dictionary.goo.ne.jp/leaf/je2/8233/m0u/おくれる
and this:
http://dictionary.goo.ne.jp/leaf/je2/8471/m0u/おそい