Hey! Interesting question! In fact it's so interesting I'm not really sure what the answer is! I'm not sure why 1a) and c) feel wrong, and I'm not even sure that they do. It's also the same with 1d) for me. I wouldn't be surprised if other people find it acceptable. I think it's something to do with the word 'plan'. If you change it to: "I offered you help", or "I offered you money" that sounds fine to me. It feels like you have to be able to 'take' the thing being offered somehow, in order to use 'offer'. For example, if you're talking about the physical document that your plan is written on, then I can imagine "I offered you my plan" would be fine. With 1b) I think the problem is that you can only use infinitives with 'offer' if the subject of the main sentence is also the subject of the infinitive. For example, "I offered to tell you my plan" or "I offered to let you consider my plan" are fine, because the subject ('I') is doing the 'offering' and the 'telling/letting'. I think 2a), b) and c) aren't right either, but for different reasons. For 2a) and c), I think the problem might just be that you can use an indirect object like that with suggest. Rather, I think it has to be like in 2d): "to you". For 2b), I think the problem is that you can't use infinitives with 'suggest'. Instead I would say: "I suggested (that) you consider my plan". Hope that helps!

I'm not an English teacher but I will do my best. Offer: To give something, to present for acceptance or rejection. Suggest: to mention an idea, possible plan or action for OTHER PEOPLE to consider. You can offer to do something for other people. You can suggest other people to do something alone or together. Suggest is kind of like asking. Because he was hunger I (offered) him my sandwich. Sandwich is a physical object not an idea. I (suggested) to him if we could eat together. Us eating together is an idea. I asked if we could eat together. I suggest we go through with my plan. the plan being eating together. You could say (I offered you a plan) because plan is the object of the sentence. You could say (I offered my idea to you) because idea is the object of the sentence. but you can't say You say I offered we eat together. because us eating together is an idea. I hope I helped.

I would just like to say although it is not entirely wrong to use "offer" You would not normally "offer a plan" - You "suggest a plan" You don't often use 'offer' in the same way as you use 'suggest' For example : You can OFFER a SUGGESTION. (both words can be used in one sentence here - that's how different they are) To offer is simply to give. (or try to give - it can be rejected) I can offer you tea, or a lift home, or yes, sometimes offer a plan or idea, But usually when offering an 'idea' - You would simply use the term "Suggest". As 'Suggestion' translates basically to "plan or idea" so in a way it's a bit silly to say you will offer someone an idea (plan) When there is already a whole english word that says that. However, while using 'offer' was not precisely incorrect, just uncommon, your grammar overall was a bit flawed. Corrections below: 1. a) *I offered you my plan. (This is slightly incorrect as it translates more like you gave away your idea instead of shared it?) b) *I offered you to consider my plan. (This would never be used) c) *I offered myself a great plan. (Also very wrong) d) I offered my plan to you. (This is about as correct as the first one, but none of these sentences would ever really be used by a native english speaker) Now these made more sense - but still had issues 2. a) I suggested you my plan. - should rather be "I suggested my plan to you." (We never use "I suggested to you, my plan". This is incorrect) b) I suggested you to consider my plan. - "I suggested that you consider my plan" c) I suggested myself a great plan. (This is completely wrong, perhaps you meant "A great plan was suggested by myself. Otherwise don't use 'myself' in that sentence form.) d) I suggested my plan to you. (this one can work fine)