Replying to salaam correctly

Q: A known person to me sometimes greet me as Assamualekum without la in it, clearly. Sometimes I reply to him in forgetfulness Walekum assalam, instead of Walekum. Then I realize that, and don't know what to read as a counteract to that. Could you please tell me what to do at that times?

Fasting while travelling

Q:

1. I have read that one can only miss his fast if one is a traveller at sehri time. What will be the ruling of an individual who is travelling abroad but his  light is at afternoon time (meaning he is still at home at sehri time)?

2. If that person needs to fast, how will he do Iftar because different countries have different iftar times.

3. Also, will putting Vicks under the nose and sniffing it throurg out the day break one's fast? I have read that it doesn't because it does not have a body. Will that have the same ruling if one was to sniff Vicks from a tissue (i.e. putting some vicks on a tissue and then inhaling the subtance form the tissue?

Taking a loan on interest

Q: I work with a company and its operate a cooperative where any employee can be saving any amount from his or her monthly salary. And one can choose to collect loan and he will pay 10% interest of the amount he collected over period of time. Then at end of every year the 10% interest collected from those people that collect loan will be shared among the people that are saving money in the cooperative including those that collected loans and paid the interest. So my question is; is the transaction halal and the interest one paid and received?