What is the rule of not using at before home? When is it optional? For example,
- When he called me I was (at) home. OK with or without.
- I am always (at) home on Sundays. OK with or without.
- He came to my place at 6pm and by that time I had already been (at) home. This doesn't make sense as it is.
- Hello! Is anyone (at) home? OK with or without.
- I am (at) home at last! OK with or without.
- I am always complimented (at) home. Here "at" is necessary.