I came across this sentence : タスクが終わったら教えてください。I don't know much about all the tenses in Japanese so I went to www.japaneseverbconjugator.com and I read that the ending たら (for the verb 終わる) is the plain form. Now I've got two questions:
1) How is the sentence balanced in terms of politeness? 終わったら is plain but 教えてください is polite. This is kind of strange for me. Whether it's all polite, whether it's all plain!
2) Is it OK if I write this? タスクが終わりましたら教えてください。
And this? タスクが終わったら教えて。