いつも and 毎回: a usual habit and each occurrence
Compare a usual choice with today’s exception and questions asked in each class, identifying the reference for repetition.
A usual pattern and its stated exception
いつも can mean always or usually. いつもは歩きますが、今日はバスに乗ります。 says that the person usually walks but will take the bus today.
この席はいつも空いています。 says that this seat is always empty. Read the strength of いつも together with any stated exception and the surrounding context.
Every occurrence of a specified activity
毎回, read まいかい, means each time an activity occurs. この授業では毎回質問します。 says that the person asks a question each time this class takes place.
三回の練習では、毎回同じ曲を弾きました。 says that the same piece was played in each of three practice sessions. The three sessions define the stated range.
Each occurrence versus each day
毎回名前を書いてください。 asks for a name to be written on every relevant occasion. Check the earlier instructions to identify the activity defining those occasions.
週に一度の授業で毎回質問します。 describes asking a question in each weekly class. Substituting every day for every class changes the basis of repetition.
How will the person travel today in いつもは歩きますが、今日はバスに乗ります。?
Show the answer and why
By bus today. Walking is the usual pattern, while 今日はバスに乗ります identifies today’s different choice.