These sentences are really quite different, despite having a similar construction. . The first one uses the phrase "To look at..." in an idiomatic way and it means "If you look at this person/thing, you will form an opinion about them/it based on their appearance, which is likely to be incorrect". It is nearly always followed by a second clause, which describes the attribute that you are likely to misjudge. In the given example, it means that he does not look 80. Other example are:
"To look at her, you'd never guess that she can run a 5-minute mile"
"To look at him, you'd never guess that he's a famous model"
"To look at it, you'd never guess that this is a championship-winning
These types of sentences can be written as :
"You would not guess that she can run a 5-minute mile by looking at
The second sentence, whilst the meaning is clear, is not good English. It can be re-written as follows:
To turn off mobile data will result in multimedia messages being
but better still is:
Turning off mobile data will result in...