if i want for may website to appear on first page for the keyword "Apple" would the use of 2 keyword combinations likes "Apple Cider", "Apple Vinegar", "Apple Juice" be enough? some SEO expert says that if i want to SEO for single keyword like "Apple" then my anchor text should also be a single keyword and it should only be "Apple" and i should avoid using 2 word combinations for my anchor text like Apple Cider. Apple Vinegar etc. because i would only be optimizing my website for Apple Cider or Apple Vinegar.
You should use the combinations aswell as just "apple". Obviously the anchor text "apple" will have a greater effect on your results for the term apple. However, if that is the only anchor text used when linking to your site then google will become suspicious - you won't get away with only using one keyword/phrase. Using the combinations will help your rankings for both the keywords, but won't have as great an effect. It's best to have around 4 keyword/phrases for your anchor texts. So using the word "apple" and the three two word combinations you've listed would be best overall ..plus you'll also be ranking for those combinations which should be a plus (assuming they are relevant to your content).
When going after a 1 word keyword, you have to expect it to take a while. So gradually build up other related rankings first. Show relevance for a range of phrases related to apples. Over time gradually mix in some links that do just say 'apple' as well. Monitor your progress for all keywords. If you reach the top for any of the longer phrases, mix in another long phrase to try to rank for. If you seem to be making progress on the 1 word phrase, put more focus on it with your link building. Keep in mind that with 1 word phrases, while great for traffic volume, they aren't usually very targeted. A 1 word phrase often covers more than one specific niche. So decide if that truly is the best traffic to target. Perhaps it would be more effective to just cover as many relevant long tail keywords as possible instead.
Like others have said, it may be worth your while to target more specific keywords to start with. Put it this way, would you search google for just 'apple' or would you be more specific to narrow your search.