Heartgard and Nexgard are totally different products. Nexgard covers ticks and fleas and no intestinal worms. Heartgard is totally opposite, it covers intestinal worms inc. heartworm but no ticks or fleas. If anything you should use them both to cover everything.

はい、可能です。カートに商品を入れる際に定期購入なしを選択してください。

24時間以内にすべて駆除されるはずです。