Question

2 questions, please help!!

Answer 1

i'd go for universal indicator, bromothymol blue and methyl red  

i mean, they have the degrees of acidity (specific color changes)  

they have wider ranges of color changes which will lead to the strength of acid  

you will know the degree of acidity of the cosmetics  

in fact, bromothymol blue is used to detect the slightest level of acid or base in a substance  

universal indicator has the pH charts; the range is big so that you can measure the level of acidity effectively  

methyl red is sensitive too as the other two mentioned earlier  

the other way that's not included in your choices is the pH meter  

unlike litmus papers which just have 2 results; either red or blue  

phenolphthalein only colorless, pale pink  

you won't know the degree of acidity  

hope that helps