Which sentences are correct?
(a) 1. Give winners an encouraging title to keep/hold their interest .
All winners get the same title eg Champ
2. Give winners encouraging titles to keep/hold their interest.
Each winner has a different title eg Spelling Star, Reading Raja
(b) 1. We use "an" with (the) words that start with a vowel sound.
'the' if you have a list of words on the board - omit if giving this as a rule for all words.
(c) 1. Some roads have a special path for people on foot.
I'm pretty sure it would be, one road, one footpath, so C2 would not be correct. (I presume you don't mean the sidewalk/footpath on every street in a city.)
Also: Which of these two is correct or more suitable for younger children?
1. Look both ways before you cross the road.
Exactly as said by every mother and by teachers in every infants classroom in the western world I'm sure!
Another version for younger children, is a more 'action' orientated directive:
Look right, look left, look right again and cross if it's clear.(-they perform it as they say it).-(in countries where people drive on the righthand side of the road)