void CreatePlayerAndUpdateDisplayName() {
    PlayFabClientAPI.LoginWithCustomID( new LoginWithCustomIDRequest {
        CustomId = "PlayFabGetPlayerProfileCustomId",
        CreateAccount = true
    }, result => {
        Debug.Log("Successfully logged in a player with PlayFabId: " + result.PlayFabId);
        UpdateDisplayName();
    }, error => Debug.LogError(error.GenerateErrorReport()));
}

void UpdateDisplayName() {
    PlayFabClientAPI.UpdateUserTitleDisplayName( new UpdateUserTitleDisplayNameRequest {
        DisplayName = "UnicornTossMaster"
    }, result => {
        Debug.Log("The player's display name is now: " + result.DisplayName);
    }, error => Debug.LogError(error.GenerateErrorReport()));
}

Successfully logged in a player with PlayFabId: SOME_PLAYFAB_ID
The player's display name is now: UnicornTossMaster

void GetPlayerProfile(string playFabId) {
    PlayFabClientAPI.GetPlayerProfile( new GetPlayerProfileRequest() {
        PlayFabId = playFabId,
        ProfileConstraints = new PlayerProfileViewConstraints() {
            ShowDisplayName = true
        }
    },
    result => Debug.Log("The player's DisplayName profile data is: " + result.PlayerProfile.DisplayName),
    error => Debug.LogError(error.GenerateErrorReport()));
}

void CreatePlayerAndUpdateDisplayName(string playFabId) {
    PlayFabClientAPI.GetPlayerProfile( new GetPlayerProfileRequest() {
        PlayFabId = playFabId,
        ProfileConstraints = new PlayerProfileViewConstraints {
            ShowDisplayName = true,
            ShowCreated = true,
            ShowLastLogin = true
        }
    },
    result => Debug.Log("The player's profile Created date is: " + result.PlayerProfile.Created),
    error => Debug.LogError(error.GenerateErrorReport()));
}

void CreatePlayerAndUpdateDisplayName(string customId) {
    PlayFabClientAPI.LoginWithCustomID( new LoginWithCustomIDRequest() {
        CustomId = customId,
        // Define info request parameters
        InfoRequestParameters = new GetPlayerCombinedInfoRequestParams() {
            // And make sure PlayerProfile is included
            GetPlayerProfile = true,
            // Define rules for PlayerProfile request
            ProfileConstraints = new PlayerProfileViewConstraints() {
                // And make sure that both AvatarUrl and LastLogin are included.
                ShowAvatarUrl = true,
                ShowLastLogin = true,
            }
        }
    },
    result =>
    {
        // Extract the data you have requested
        var avatarUrl = result.InfoResultPayload.PlayerProfile.AvatarUrl;
    },
    error => Debug.LogError(error.GenerateErrorReport()));
}