#1 is a poorly worded sentence whose meaning is not clear. Here are some possible interpretations: 1) The increase reported is the strongest ever reported in any year. The period to which the "increase" applies is not specified. 2) Not since one year ago has such a strong increase been reported. 3) The total increase during a one year period in the number of employees at this bank was the strongest, as compared to other banks. ...and so forth. Don't try hard to understand this sentence because it is so bad. The phrase "for a year" can modify "strongest", "increase", or "appointments". The only way to determine what it modifies is to ask the author what he meant to say. As for the second question, there is no difference other than the fact that (b) supplies an indirect object, making the meaning a little bit more clear.

1 The strongest increase… 2 Both ok but the first it more UK and the second more US.

Thank Mr Johann very much for often helping me so carefully and patiently. You are one of my best teaches I have met in this italki place.

The statement in 1 uses British English (presumably correctly given the source) and isn’t entirely clear to American English speakers (for whom it isn’t intended) because we don’t commonly use the phrase ‘permanent appointments’ and we would use a different way to express ‘for a year’. Language use is ‘good’ or ‘poor’ based on its ability to fulfill a task. People who want to fully understand Bank of Scotland publications need to learn some English. That’s true, but to different degrees, whether your native language is Chinese, American English or British English.

It happened (for a year). modifies the verb.