i would highly suggest starting with a 1/4 strength nute application.... see how your plant reacts.. and increase from there on.. i wouldnt go over 1/2 strength tho... all purpose feeds have a tendency to nute burn in high applications...
i do agree with alternating feedings... more so for the fact that different nutes are used in different amounts.. it is very possible to still have nutes left that are unused when you go to feed again.. alternating between plain water and nute water will allow your plant to use up most of the nutes that are left.. this is lessen the risk of nute burn later...
it has LITTLE affect on the soil ph.. it is true that build up in the soil from salts can lower the ph, not raise it... so an alternating feeding schedule can help lower the risk of build up as well.. but it wont have any real affects on the soils ph....
you can use the nutes you have throughout the entire grow.. both veg and flower... but all purpose feeds arent the best to use to begin with.. again, as i said, nutes are used in different amounts... using a 2 or 3 part system, that has a specific grow and bloom formula, and a micro formula on the 3 parts, helps ensure your plant is getting only what it needs when it needs it.. all purpose feeds can over load your plant if you arent careful.. but watching the amount of nutes you use and how your plant reacts to them will tell you if you have over fed...
if you are looking for a good nute program.. here are some names of the best on the market.. all of them carry a 2 and 3 part system depending on how much work you want to do... and plenty of additives if you want to spend a little extra on "all the bells and whistles".. and all can work in either soil, hydro, or soiless mixes...
fox farms
general hydroponics (this is what i use.. great results)
advanced nutrients
technaflora/bc line
there are others out there also... just do some research to find what you think will work best for you...